Release 5.0.0

What does this MR do?

Squash changelog for v5 RCs as suggested in gitlab-org/gitlab#455488 (comment 1888364515) and release the final 5.0.0 version.

What are the relevant issue numbers?

gitlab-org/gitlab#455488 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer